Tree-killing Hemlock Woolly Adelgids Hitch Rides on Birds

At first glance, you might not think these little bits of fluff could pose much of a threat. But, like Star Trek’s troublesome tribbles, hemlock woolly adelgids (Adelges tsugae) can quickly multiply and wreak havoc. When these tiny sap-sucking insects were introduced to the forests of the Northeastern United States, they lacked an effective predator and within a few decades they caused significant die-offs of eastern hemlocks (Tsuga canadensis) and Carolina hemlocks (Tsuga caroliniana) — trees that are both economically and ecologically important to eastern forests. Woolly adelgids were clearly destructive, and they were spreading, but it wasn’t clear exactly how they were spreading.